While the east coast braces itself for potentially one of the strongest storms on record, Winter Storm Watches and Blizzard Watches are starting to appear in the Mid-Atlantic.
Energy currently centered across the Rockies will continue to dip south, through the Tennessee Valley and make a turn towards the northeast. That is where things get interesting…and difficult. Where the storm heads from there – tracking close to the coast or further out to sea – will directly impact the amount of snow to fall across the region. Nonetheless, there will be times during this storm when blizzard-conditions will exist, especially across eastern Pennsylvania, New Jersey, and the Delmarva. Blizzard conditions are defined as snow or blowing snow, winds in excess of 35 miles per hour and visibilities less than 1/4 of a mile all for 3 consecutive hours.
Models continue to fluctuate in and out of consensus with each other, with most dropping over a foot of snow along the I-95 corridor from Washington DC to Philadelphia. While there are many factors that favor this heavy, historic thumping, snow lovers should be warned of two potential buzz-kills.
Areas of red show warming air about a mile up in the atmosphere. This could translate to a layer above freezing, thus melting the snow before it hits the ground.
First off, is the dreaded rain-snow line. As the surface low develops to the east of the Delmarva, strong easterly winds will drive onshore. With sea surface temperatures approaching 50 degrees, warm waters will heat up the shallow layer of air and change the snow over to rain for much of New Jersey, Delaware, the eastern shore of Maryland, and even into southeastern Pennsylvania. In addition, incredibly strong winds whipping from the south around the area of low pressure will produce a warm surge that will support this potential changeover.
A depiction of a dry slot getting wrapped into the system. These areas see significantly less precipitation than most other areas.
A second limitation to watch out for is the development of a dry slot. Dry slots are areas of dry air that get wrapped within the storm, and generally seen in nor’Easters. If verified, this would greatly reduce the potential snowfall for this system across these areas.
While snow totals may underachieve in some areas and exceed expectations in others, there is no doubt power outages will be a major concern. Heavy wet snow built up on branches will snap and trees may all-out topple over in sustained winds of 30 miles per hour gusting to 60 miles per hour.
Now my thoughts…. Exactly predicting a dry slot is like nailing Jell-O to the wall. Until the system forms, and approaches the region, it is very difficult to tell if the dry slot will form and where this will be. I do think much of the area within 100 miles of the coast will switch over to rain or sleet. Further west, a deformation band – an enhanced area of snow – will form….that will be the big money winner.